So far, there have been two types of DC generators and motors, all of which must have a reversing device. One type is to use an electric brush to reverse, and the other type is to use a semiconductor switch element to reverse. The former has simple structure, low cost, fast wearing of electric brush, and short life; while the latter has complex structure, high cost and long life.
The aim of the present invention is to realize a DC generator and motor without any reversing element, which has simple structure, low cost and long life.